Smokeless Shootist and Smokeless Duelist are the traditional 2 revolvers, rifle and shotgun.
Working Cowboy is a revolver and rifle, shot using any style hold or powder.
The Originals were conceived as any two NCOWS legal firearms shot using powder appropriate to the date of the persona and firearms used, but after several years of experience shooting the class most all end up using a revolver and rifle. As Senator Books O'Toole pointed out, the few instances where someone used another combination, it was a scoring nightmare. How do you score shooting when someone uses, say, two shotguns and everyone else a revolver and rifle? For this reason there is a motion before the Congress to officially make the class a one revolver and a rifle, which makes it similar as Working Cowboy but with the addition of juried documentation of your persona by your peers. The Originals assumes a duelist hold would be used, as that was the shooting style taught in the 19th century, but I don't believe there is any wording prescribing such in the rules.
Pistoleer is another 2 revolver, rifle and shotgun class, but restrictions to use of early firearms, pre 1872, and use of black powder and duelist hold.
By all means, we'd love to have you as a member, and you're right to go slow, - and you'll be able to get a lot of helpful tips from our membership on outfitting. Our Convention in March in Kansas City is a good place to do some bargain shopping, too.
RCJ